// MIT License

// Copyright (c) 2019 Erin Catto

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#include "test.h"
#include "imgui/imgui.h"

// This shows how to use sensor shapes. Sensors don't have collision, but report overlap events.
class Sensors : public Test
{
public:

  enum
  {
    e_count = 7
  };

  Sensors()
  {
    {
      b2BodyDef bd;
      b2Body* ground = m_world->CreateBody(&bd);

      {
        b2EdgeShape shape;
        shape.SetTwoSided(b2Vec2(-40.0f, 0.0f), b2Vec2(40.0f, 0.0f));
        ground->CreateFixture(&shape, 0.0f);
      }

#if 0
      {
        b2FixtureDef sd;
        sd.SetAsBox(10.0f, 2.0f, b2Vec2(0.0f, 20.0f), 0.0f);
        sd.isSensor = true;
        m_sensor = ground->CreateFixture(&sd);
      }
#else
      {
        b2CircleShape shape;
        shape.m_radius = 5.0f;
        shape.m_p.Set(0.0f, 10.0f);

        b2FixtureDef fd;
        fd.shape = &shape;
        fd.isSensor = true;
        m_sensor = ground->CreateFixture(&fd);
      }
#endif
    }

    {
      b2CircleShape shape;
      shape.m_radius = 1.0f;

      for (int32 i = 0; i < e_count; ++i)
      {
        b2BodyDef bd;
        bd.type = b2_dynamicBody;
        bd.position.Set(-10.0f + 3.0f * i, 20.0f);
        bd.userData.pointer = i;

        m_touching[i] = false;
        m_bodies[i] = m_world->CreateBody(&bd);

        m_bodies[i]->CreateFixture(&shape, 1.0f);
      }
    }

    m_force = 100.0f;
  }

  // Implement contact listener.
  void BeginContact(b2Contact* contact) override
  {
    b2Fixture* fixtureA = contact->GetFixtureA();
    b2Fixture* fixtureB = contact->GetFixtureB();

    if (fixtureA == m_sensor)
    {
      uintptr_t index = fixtureB->GetBody()->GetUserData().pointer;
      if (index < e_count)
      {
        m_touching[index] = true;
      }
    }

    if (fixtureB == m_sensor)
    {
      uintptr_t index = fixtureA->GetBody()->GetUserData().pointer;
      if (index < e_count)
      {
        m_touching[index] = true;
      }
    }
  }

  // Implement contact listener.
  void EndContact(b2Contact* contact) override
  {
    b2Fixture* fixtureA = contact->GetFixtureA();
    b2Fixture* fixtureB = contact->GetFixtureB();

    if (fixtureA == m_sensor)
    {
      uintptr_t index = fixtureB->GetBody()->GetUserData().pointer;
      if (index < e_count)
      {
        m_touching[index] = false;
      }
    }

    if (fixtureB == m_sensor)
    {
      uintptr_t index = fixtureA->GetBody()->GetUserData().pointer;
      if (index < e_count)
      {
        m_touching[index] = false;
      }
    }
  }

  void UpdateUI() override
  {
    ImGui::SetNextWindowPos(ImVec2(10.0f, 100.0f));
    ImGui::SetNextWindowSize(ImVec2(200.0f, 60.0f));
    ImGui::Begin("Sensor Controls", nullptr, ImGuiWindowFlags_NoMove | ImGuiWindowFlags_NoResize);

    ImGui::SliderFloat("Force", &m_force, 0.0f, 2000.0f, "%.0f");

    ImGui::End();
  }

  void Step(Settings& settings) override
  {
    Test::Step(settings);

    // Traverse the contact results. Apply a force on shapes
    // that overlap the sensor.
    for (int32 i = 0; i < e_count; ++i)
    {
      if (m_touching[i] == false)
      {
        continue;
      }

      b2Body* body = m_bodies[i];
      b2Body* ground = m_sensor->GetBody();

      b2CircleShape* circle = (b2CircleShape*)m_sensor->GetShape();
      b2Vec2 center = ground->GetWorldPoint(circle->m_p);

      b2Vec2 position = body->GetPosition();

      b2Vec2 d = center - position;
      if (d.LengthSquared() < FLT_EPSILON * FLT_EPSILON)
      {
        continue;
      }

      d.Normalize();
      b2Vec2 F = m_force * d;
      body->ApplyForce(F, position, false);
    }
  }

  static Test* Create()
  {
    return new Sensors;
  }

  b2Fixture* m_sensor;
  b2Body* m_bodies[e_count];
  float m_force;
  bool m_touching[e_count];
};

static int testIndex = RegisterTest("Collision", "Sensors", Sensors::Create);
